In the manufacture of paper on continuous papermaking machines, a web of paper is formed from an aqueous suspension of fibers (stock) on a traveling mesh of papermaking fabric and water drains by gravity and suction through the fabric. The web is then transferred to the pressing section where more water is removed by pressure and vacuum. The web next enters the dryer section where steam heated dryers and hot air completes the drying process. The paper machine is, in essence, a water removal, system. A typical forming section of a papermaking machine includes an endless traveling papermaking fabric or wire, which travels over a series of water removal elements such as table rolls, foils, vacuum foils, and suction boxes. The stock is carried on the top surface of the papermaking fabric and is de-watered as the stock travels over successive de-watering elements to form a sheet of paper. Finally, the wet sheet is transferred to the press section of the papermaking machine where enough water is removed to form a sheet of paper. Many factors affect the quality of the paper produced.
The presence of defects and holes in the papermaking process can be disastrous since even a small hole can catch to result in a roll tear. Most of paper defects are repetitive but if the causes of the defects are not identified and corrected quickly the equipment damage can be extensive, which requires time consuming shut downs and expensive repairs. Current web inspection systems (WIS) can deliver quality data to support decisions that need to be made in subsequent processing steps. Based on web inspection technology, all relevant process images and data are captured and analyzed on-line. Interlinking WIS with events capturing already exists where, in addition to the defects detected, the WIS system also displays the corresponding video sequences recorded by cameras. Unfortunately, existing WISs do not include root cause analysis for repetitive defects which identifies the nature of web sheet defects, their locations relative to the papermaking machine, and the specific sources or names of the equipment that caused the defects. There are no solutions available for non-repetitive defects.